lib/mac-learning.c

   1 /*
   2  * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "mac-learning.h"
  19
  20 #include <inttypes.h>
  21 #include <stdlib.h>
  22
  23 #include "bitmap.h"
  24 #include "coverage.h"
  25 #include "hash.h"
  26 #include "list.h"
  27 #include "poll-loop.h"
  28 #include "timeval.h"
  29 #include "unaligned.h"
  30 #include "util.h"
  31 #include "vlan-bitmap.h"
  32
  33 COVERAGE_DEFINE(mac_learning_learned);
  34 COVERAGE_DEFINE(mac_learning_expired);
  35
  36 /* Returns the number of seconds since 'e' (within 'ml') was last learned. */
  37 int
  38 mac_entry_age(const struct mac_learning *ml, const struct mac_entry *e)
  39 {
  40     time_t remaining = e->expires - time_now();
  41     return ml->idle_time - remaining;
  42 }
  43
  44 static uint32_t
  45 mac_table_hash(const struct mac_learning *ml, const uint8_t mac[ETH_ADDR_LEN],
  46                uint16_t vlan)
  47 {
  48     return hash_mac(mac, vlan, ml->secret);
  49 }
  50
  51 static struct mac_entry *
  52 mac_entry_from_lru_node(struct list *list)
  53 {
  54     return CONTAINER_OF(list, struct mac_entry, lru_node);
  55 }
  56
  57 static struct mac_entry *
  58 mac_entry_lookup(const struct mac_learning *ml,
  59                  const uint8_t mac[ETH_ADDR_LEN], uint16_t vlan)
  60 {
  61     struct mac_entry *e;
  62
  63     HMAP_FOR_EACH_WITH_HASH (e, hmap_node, mac_table_hash(ml, mac, vlan),
  64                              &ml->table) {
  65         if (e->vlan == vlan && eth_addr_equals(e->mac, mac)) {
  66             return e;
  67         }
  68     }
  69     return NULL;
  70 }
  71
  72 /* If the LRU list is not empty, stores the least-recently-used entry in '*e'
  73  * and returns true.  Otherwise, if the LRU list is empty, stores NULL in '*e'
  74  * and return false. */
  75 static bool
  76 get_lru(struct mac_learning *ml, struct mac_entry **e)
  77     OVS_REQ_RDLOCK(ml->rwlock)
  78 {
  79     if (!list_is_empty(&ml->lrus)) {
  80         *e = mac_entry_from_lru_node(ml->lrus.next);
  81         return true;
  82     } else {
  83         *e = NULL;
  84         return false;
  85     }
  86 }
  87
  88 static unsigned int
  89 normalize_idle_time(unsigned int idle_time)
  90 {
  91     return (idle_time < 15 ? 15
  92             : idle_time > 3600 ? 3600
  93             : idle_time);
  94 }
  95
  96 /* Creates and returns a new MAC learning table with an initial MAC aging
  97  * timeout of 'idle_time' seconds and an initial maximum of MAC_DEFAULT_MAX
  98  * entries. */
  99 struct mac_learning *
 100 mac_learning_create(unsigned int idle_time)
 101 {
 102     struct mac_learning *ml;
 103
 104     ml = xmalloc(sizeof *ml);
 105     list_init(&ml->lrus);
 106     hmap_init(&ml->table);
 107     ml->secret = random_uint32();
 108     ml->flood_vlans = NULL;
 109     ml->idle_time = normalize_idle_time(idle_time);
 110     ml->max_entries = MAC_DEFAULT_MAX;
 111     ml->need_revalidate = false;
 112     ovs_refcount_init(&ml->ref_cnt);
 113     ovs_rwlock_init(&ml->rwlock);
 114     return ml;
 115 }
 116
 117 struct mac_learning *
 118 mac_learning_ref(const struct mac_learning *ml_)
 119 {
 120     struct mac_learning *ml = CONST_CAST(struct mac_learning *, ml_);
 121     if (ml) {
 122         ovs_refcount_ref(&ml->ref_cnt);
 123     }
 124     return ml;
 125 }
 126
 127 /* Unreferences (and possibly destroys) MAC learning table 'ml'. */
 128 void
 129 mac_learning_unref(struct mac_learning *ml)
 130 {
 131     if (ml && ovs_refcount_unref(&ml->ref_cnt) == 1) {
 132         struct mac_entry *e, *next;
 133
 134         HMAP_FOR_EACH_SAFE (e, next, hmap_node, &ml->table) {
 135             hmap_remove(&ml->table, &e->hmap_node);
 136             free(e);
 137         }
 138         hmap_destroy(&ml->table);
 139
 140         bitmap_free(ml->flood_vlans);
 141         ovs_rwlock_destroy(&ml->rwlock);
 142         free(ml);
 143     }
 144 }
 145
 146 /* Provides a bitmap of VLANs which have learning disabled, that is, VLANs on
 147  * which all packets are flooded.  Returns true if the set has changed from the
 148  * previous value. */
 149 bool
 150 mac_learning_set_flood_vlans(struct mac_learning *ml,
 151                              const unsigned long *bitmap)
 152 {
 153     if (vlan_bitmap_equal(ml->flood_vlans, bitmap)) {
 154         return false;
 155     } else {
 156         bitmap_free(ml->flood_vlans);
 157         ml->flood_vlans = vlan_bitmap_clone(bitmap);
 158         return true;
 159     }
 160 }
 161
 162 /* Changes the MAC aging timeout of 'ml' to 'idle_time' seconds. */
 163 void
 164 mac_learning_set_idle_time(struct mac_learning *ml, unsigned int idle_time)
 165 {
 166     idle_time = normalize_idle_time(idle_time);
 167     if (idle_time != ml->idle_time) {
 168         struct mac_entry *e;
 169         int delta;
 170
 171         delta = (int) idle_time - (int) ml->idle_time;
 172         LIST_FOR_EACH (e, lru_node, &ml->lrus) {
 173             e->expires += delta;
 174         }
 175         ml->idle_time = idle_time;
 176     }
 177 }
 178
 179 /* Sets the maximum number of entries in 'ml' to 'max_entries', adjusting it
 180  * to be within a reasonable range. */
 181 void
 182 mac_learning_set_max_entries(struct mac_learning *ml, size_t max_entries)
 183 {
 184     ml->max_entries = (max_entries < 10 ? 10
 185                        : max_entries > 1000 * 1000 ? 1000 * 1000
 186                        : max_entries);
 187 }
 188
 189 static bool
 190 is_learning_vlan(const struct mac_learning *ml, uint16_t vlan)
 191 {
 192     return !ml->flood_vlans || !bitmap_is_set(ml->flood_vlans, vlan);
 193 }
 194
 195 /* Returns true if 'src_mac' may be learned on 'vlan' for 'ml'.
 196  * Returns false if 'ml' is NULL, if src_mac is not valid for learning, or if
 197  * 'vlan' is configured on 'ml' to flood all packets. */
 198 bool
 199 mac_learning_may_learn(const struct mac_learning *ml,
 200                        const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 201 {
 202     return ml && is_learning_vlan(ml, vlan) && !eth_addr_is_multicast(src_mac);
 203 }
 204
 205 /* Searches 'ml' for and returns a MAC learning entry for 'src_mac' in 'vlan',
 206  * inserting a new entry if necessary.  The caller must have already verified,
 207  * by calling mac_learning_may_learn(), that 'src_mac' and 'vlan' are
 208  * learnable.
 209  *
 210  * If the returned MAC entry is new (as may be determined by calling
 211  * mac_entry_is_new()), then the caller must pass the new entry to
 212  * mac_learning_changed().  The caller must also initialize the new entry's
 213  * 'port' member.  Otherwise calling those functions is at the caller's
 214  * discretion. */
 215 struct mac_entry *
 216 mac_learning_insert(struct mac_learning *ml,
 217                     const uint8_t src_mac[ETH_ADDR_LEN], uint16_t vlan)
 218 {
 219     struct mac_entry *e;
 220
 221     e = mac_entry_lookup(ml, src_mac, vlan);
 222     if (!e) {
 223         uint32_t hash = mac_table_hash(ml, src_mac, vlan);
 224
 225         if (hmap_count(&ml->table) >= ml->max_entries) {
 226             get_lru(ml, &e);
 227             mac_learning_expire(ml, e);
 228         }
 229
 230         e = xmalloc(sizeof *e);
 231         hmap_insert(&ml->table, &e->hmap_node, hash);
 232         memcpy(e->mac, src_mac, ETH_ADDR_LEN);
 233         e->vlan = vlan;
 234         e->grat_arp_lock = TIME_MIN;
 235         e->port.p = NULL;
 236     } else {
 237         list_remove(&e->lru_node);
 238     }
 239
 240     /* Mark 'e' as recently used. */
 241     list_push_back(&ml->lrus, &e->lru_node);
 242     e->expires = time_now() + ml->idle_time;
 243
 244     return e;
 245 }
 246
 247 /* Changes 'e''s tag to a new, randomly selected one.  Causes
 248  * mac_learning_run() to flag for revalidation the tag that would have been
 249  * previously used for this entry's MAC and VLAN (either before 'e' was
 250  * inserted, if it is new, or otherwise before its port was updated.)
 251  *
 252  * The client should call this function after obtaining a MAC learning entry
 253  * from mac_learning_insert(), if the entry is either new or if its learned
 254  * port has changed. */
 255 void
 256 mac_learning_changed(struct mac_learning *ml)
 257 {
 258     COVERAGE_INC(mac_learning_learned);
 259     ml->need_revalidate = true;
 260 }
 261
 262 /* Looks up MAC 'dst' for VLAN 'vlan' in 'ml' and returns the associated MAC
 263  * learning entry, if any.  If 'tag' is nonnull, then the tag that associates
 264  * 'dst' and 'vlan' with its currently learned port will be OR'd into
 265  * '*tag'. */
 266 struct mac_entry *
 267 mac_learning_lookup(const struct mac_learning *ml,
 268                     const uint8_t dst[ETH_ADDR_LEN], uint16_t vlan)
 269 {
 270     if (eth_addr_is_multicast(dst)) {
 271         /* No tag because the treatment of multicast destinations never
 272          * changes. */
 273         return NULL;
 274     } else if (!is_learning_vlan(ml, vlan)) {
 275         /* We don't tag this property.  The set of learning VLANs changes so
 276          * rarely that we revalidate every flow when it changes. */
 277         return NULL;
 278     } else {
 279         struct mac_entry *e = mac_entry_lookup(ml, dst, vlan);
 280
 281         ovs_assert(e == NULL || e->port.p != NULL);
 282         return e;
 283     }
 284 }
 285
 286 /* Expires 'e' from the 'ml' hash table. */
 287 void
 288 mac_learning_expire(struct mac_learning *ml, struct mac_entry *e)
 289 {
 290     hmap_remove(&ml->table, &e->hmap_node);
 291     list_remove(&e->lru_node);
 292     free(e);
 293 }
 294
 295 /* Expires all the mac-learning entries in 'ml'.  If not NULL, the tags in 'ml'
 296  * are added to 'tags'.  Otherwise the tags in 'ml' are discarded.  The client
 297  * is responsible for revalidating any flows that depend on 'ml', if
 298  * necessary. */
 299 void
 300 mac_learning_flush(struct mac_learning *ml)
 301 {
 302     struct mac_entry *e;
 303     while (get_lru(ml, &e)){
 304         ml->need_revalidate = true;
 305         mac_learning_expire(ml, e);
 306     }
 307     hmap_shrink(&ml->table);
 308 }
 309
 310 /* Does periodic work required by 'ml'.  Returns true if something changed that
 311  * may require flow revalidation. */
 312 bool
 313 mac_learning_run(struct mac_learning *ml)
 314 {
 315     bool need_revalidate;
 316     struct mac_entry *e;
 317
 318     while (get_lru(ml, &e)
 319            && (hmap_count(&ml->table) > ml->max_entries
 320                || time_now() >= e->expires)) {
 321         COVERAGE_INC(mac_learning_expired);
 322         ml->need_revalidate = true;
 323         mac_learning_expire(ml, e);
 324     }
 325
 326     need_revalidate = ml->need_revalidate;
 327     ml->need_revalidate = false;
 328     return need_revalidate;
 329 }
 330
 331 void
 332 mac_learning_wait(struct mac_learning *ml)
 333 {
 334     if (hmap_count(&ml->table) > ml->max_entries
 335         || ml->need_revalidate) {
 336         poll_immediate_wake();
 337     } else if (!list_is_empty(&ml->lrus)) {
 338         struct mac_entry *e = mac_entry_from_lru_node(ml->lrus.next);
 339         poll_timer_wait_until(e->expires * 1000LL);
 340     }
 341 }